Heat generated by electronic devices and circuitry must be dissipated to improve reliability and prevent premature failure. Remote Radio Unit (RRU), Digital Unit (DU) and microwave communication device are examples of telecommunication equipment that need heat dissipation to reduce their temperature. As one important member in Radio Base Station (RBS) product family, RRU is widely deployed. However, RRU with high coverage generates large amount heat, which will decrease its reliability due to high temperature.
Techniques for heat dissipation include natural cooling and forced cooling. Natural cooling needs no extra devices or energy input. It is featured with low airflow rate, bulky heat sinks, energy saving and noise-free environment. Typically, a heat sink consists of a metal plate with one or more flat surfaces to ensure good thermal contact with the components to be cooled, and an array of comb or fin like protrusions to increase the surface contacting with the air. The high thermal conductivity of the metal combined with its large surface area result in the rapid transfer of thermal energy to the surrounding.
RRU is usually installed near antenna, and thus for easy installation, it shall be designed to be as compact and light as possible. However, heat sinks impose a severe restriction on RRU in terms of volume and weight, and in this sense, natural cooling is unsatisfied.
A heat sink is sometimes used in conjunction with a fan to increase the rate of airflow over the heat sink and a larger temperature gradient is maintained by replacing warmed air faster than convection would. As a result, a compact heat sink is available. This is known as forced cooling approach. However, it is featured with high energy consumption and high acoustic noise level. For some base stations with forced cooling mechanism, their sound power levels can reach at 79 dBA, which is harmful to health. Often, RRUs are necessarily installed near residential areas where their noise level shall be strictly controlled. In such a case, these RRUs have to be equipped with bulky heat sinks. As for the forced cooling, another issue involves in fan failure, which is a fatal menace for RRUs.